CAR T-Cell Therapy: Where are We Today?

CAR T-cell therapy works by generating cancer-specific T-cells to fight a patient’s unique form of cancer. Image credit: Wikipedia.org

What progress is being made today in the field of CAR T-cell therapy, and what can we expect moving forward? These questions and others were addressed in a recent BioInsights webinar presented by renowned cancer biologist Dr. Isabelle Rivière. [1]

CAR T-cell therapy has been generating remarkable results in the fight to cure cancer. The development of this cell-based therapy from the lab to the clinic hasn’t all been smooth sailing, however. Serious side effects and even deaths have occurred in some clinical trials. These tragic set-backs have prompted a great deal of caution and vigilance in the field. Overall, though, there is still great optimism. CAR T-cell trials have yielded impressive results in the treatment of blood cancers such as leukemia and B cell lymphoma. In certain studies, for example, up to 90 percent of children and adults with an “untreatable” acute form of leukemia achieved remission after receiving CAR T-cell therapy. Each successive generation of CAR T-cell products has sought to minimize complications while maximizing the effectiveness of treatment.

Dr. Rivière works at the Memorial Sloan Kettering Cancer Center. In her role as Director of the Center’s Cell Therapy and Cell Engineering Facility, she has had personal input into an unusually high number of CAR T clinical trials, and consequently has a good feel for the basic issues and challenges of CAR T-cell therapy.

One of the most critical components in any CAR T therapy is the manufacturing platform. A manufacturing platform acts like a roadmap for developing a finished product. The first step is to establish a general overview of what you need to do; once that’s in place, you can work out specific methods for each step along the way.

CAR T therapy starts with the patient; cells are collected through apheresis; the process of collecting a blood sample, then separating out the cells from the plasma. Cells are usually cryopreserved at this point until they can be handled further. Once the lab is ready to proceed, cells are thawed and washed, and T-cells are purified from the mixture. The T-cells are activated, genetically modified, expanded to increase cell numbers to an appropriate dose, then cryopreserved for storage or shipment. On the day of treatment, cells are thawed, and finally, administered to the patient.

Dr. Rivière stresses that to get good results, you must first truly understand how immune cells work. The “core hypothesis” of CAR T-cell therapy is that a person’s own T-cells can be directed to specifically target the form of cancer from which they are suffering. Therefore, to “make” a CAR T-cell, the patient’s own T-cells are first modified to recognize specific markers on a cancer cell. The first generation of CAR T therapies focused on CD8+ T-cells, while second and third generation CAR T therapies include T-cells that target additional cancer cell markers, include additional signalling domains, and generally offer advanced T-cell function. In Dr. Rivière’s lab, her group works with third generation “CD19 targeting” CAR T-cells. These cells are genetically modified with higher activation and proliferation capabilities than cells tested in earlier clinical trials. In one Phase 1 clinical study focused on treating acute leukemia, physicians achieved complete remission in 77-90% of the patients treated with the CD19-targeting CAR T-cell. This particular CAR T drug has received special designation as a “breakthrough therapy” by the FDA, meaning that it will be subject to an accelerated approval process as the trial continues.

While increasing activation and proliferation can improve the effectiveness of CAR T therapy, other potential improvements are also being examined. Researchers are working on ways to enhance the T-cell’s ability to overcome methods by which cancer cells “hide” from the immune system, as well as ways to improve CAR T-cell selectivity, targeting, survival and expansion rates. By way of example, Dr. Rivière’s lab was recently working on ways to get better incorporation of modifying genes into the T-cells. An effective way to do this is to deplete the original cellular material of CD14 cells, which is achieved using magnetic beads. Dr. Rivière’s group was able to increase gene transduction by using biotech company Miltenyi’s new TransACT beads rather than traditional Dynabeads. Their lab is also looking at which growth factors and nutrients are best to keep CAR T-cells healthy during expansion. Each small step is important, and there are many ways to increase overall efficacy of a final product.

Optimizing the manufacturing platform is just as important as optimizing the cells. Dr. Rivière firmly believes that an integrated and automated platform is critical to achieving high quality, consistent products in cell therapy manufacturing. Her own lab takes advantage of Miltenyi’s CliniMACS Prodigy® System, a popular choice in the cell therapy field due to the fact that the system integrates many of the necessary manufacturing steps into one instrument. Dr. Rivière’s group have used T-cells isolated from both fresh and cryopreserved apheresis products, and found that they can achieve similar high purity (between 90-97%) results from each. While initial cell recovery is somewhat higher for cells isolated from fresh apheresis product, she finds that cell viability is high (over 80%) in all cases, and was easily able to use the Prodigy system to reach cell numbers equivalent to normal patient doses.

Dr. Rivière is a strong advocate of automated manufacturing platforms, and of automated methods in general. She enumerates the benefits of automation during both manufacturing and downstream cell therapy processes: better process control, higher throughput, product consistency, and reproducibility. We have previously discussed different methods of automating various cell therapy processes, and how these methods help bring down costs as cell therapies are approved and commercialized. Automating last mile processes such as drug delivery and administration is worth a special mention here, because while these activities are necessarily separate from the actual manufacturing process, they are just as critical. Point-of-care facilities like hospitals and clinics are ultimately responsible for making sure a live therapeutic such as a CAR T-cell therapy reaches a patient without being compromised. That includes ensuring that the cells are thawed by a method that guarantees consistency and reproducible efficacy. In this we recommend using an automated thawing device such as our own ThawSTAR® cell thawing system.

Going forward, Dr. Rivière fully expects that CD19 CAR T-cells will be approved in the near future, and that this will open things up for similar products to be approved. While her own research has focused on finding cures for blood cancers such as leukemia, she would very much like to see more research on adapting CAR-T-cells to treat solid tumors, and expects that in this way, the field of CAR T-cell therapy will continue to expand and grow.